refactor: restructure services and add image/pdf extraction utilities

- Add image_extractor, pdf_downloader, pi_client, trends services
- Add shared utils module
- Refactor summarizer, embedder, routes for cleaner separation
- Update tests to match new service structure

app/models.py

@@ -1,4 +1,4 @@
-"""SQLAlchemy ORM 模型 — papers, authors, tags, summaries, FTS5, logs, locks, user data。"""
+"""SQLAlchemy ORM 模型 — papers, authors, tags, summaries, user data, logs, locks。"""
 
 from datetime import date, datetime
 
@@ -13,7 +13,6 @@ from sqlalchemy import (
     String,
     Text,
     UniqueConstraint,
-    text,
 )
 from sqlalchemy.orm import relationship
 
@@ -204,32 +203,3 @@ class DataDeleteJob(Base):
     error = Column(Text)
     started_at = Column(DateTime, nullable=False)
     completed_at = Column(DateTime)
-
-
-# ── FTS5 索引初始化 SQL（普通虚拟表，由应用层维护）──────────────────────
-FTS5_CREATE_SQL = """
-CREATE VIRTUAL TABLE IF NOT EXISTS papers_fts USING fts5(
-    title_en,
-    title_zh,
-    abstract,
-    authors,
-    tags,
-    summary_text,
-    tokenize='unicode61'
-);
-"""
-
-FTS5_TRIGGER_INDEX = """
--- partial index for task_locks running
-CREATE UNIQUE INDEX IF NOT EXISTS uq_task_locks_running
-ON task_locks(task, lock_key) WHERE status = 'running';
-"""
-
-
-def init_db(engine):
-    """创建所有 ORM 表 + FTS5 虚拟表。"""
-    Base.metadata.create_all(engine)
-    with engine.connect() as conn:
-        conn.execute(text(FTS5_CREATE_SQL))
-        conn.execute(text(FTS5_TRIGGER_INDEX))
-        conn.commit()